Hi,
as i'm reviewing the way we manage the WAL (Write Ahead Log), I have a
few questions :
1) UserLogRecord
It's a data structure encapsulating an opaque byte[] containing a
serialized form of a record. We have two length, the serialized data
length, and the buffer length (which might be wider).
I guess that the rational is that we first allocate a buffer, and we may
store some smaller data into this buffer. Sounds ok, but the question is
why we can't simply store a full buffer (ie only allocate what we need)?
Am I missing something here ?
2) LogEdit
When we write the LogEdit instance, we have no way to read them back as
we don't know if we have written a TxnChangeState or a
DataChangeContainer. Even for a DataChangeContainer, which contains a
list of DataChange (ie either IndexModification or EntryModification),
we have no indication about the written type.
I think we need to add an identifier at the begining of the written data
structure to allow the reader to know which kind of object to create, or
again, I'm missing something (like we will always know what kind of
object we are expecting, because they are ordered - unlikely for
indexChange, as we will have a variable number of modified indexes -.
3) Reading the log
I guess we never read the log, so far. Am I right ? Is this a part of
the code we need to implement ?
Any clues ?
Thanks !
--
Regards,
Cordialement,
Emmanuel Lécharny
www.iktek.com
